Multiparametric MRI and CT Models of Infarct Core and Favorable Penumbral Imaging Patterns in Acute Ischemic Stroke

Abstract

Background and Purpose Objective imaging methods to identify optimal candidates for late recanalization therapies are needed. The study goals were 1) to develop MRI and CT multiparametric, voxel-based predictive models of infarct core and penumbra in acute ischemic stroke patients, and 2) to develop patient-level imaging criteria for favorable penumbral pattern based on good clinical outcome in response to successful recanalization. Methods An analysis of imaging and clinical data was performed on two cohorts of patients (one screened with CT, the other with MRI) who underwent successful treatment for large vessel, anterior circulation stroke. Subjects were divided 2:1 into derivation and validation cohorts. Pretreatment imaging parameters independently predicting final tissue infarct and final clinical outcome were identified. Results The MRI and CT models were developed and validated from 34 and 32 patients, employing 943,320 and 1,236,917 voxels respectively. The derivation MRI and two-branch CT models had an overall accuracy of 74% and 80% respectively, and were independently validated with an accuracy of 71% and 79% respectively. The imaging criteria of 1) predicted infarct core ≤ 90 mL and 2) ratio of predicted infarct tissue within the at-risk region ≤ 70% identified patients as having a favorable penumbral pattern with 78–100% accuracy. Conclusions Multiparametric voxel-based MRI and CT models were developed to predict the extent of infarct core and overall penumbral pattern status in patients with acute ischemic stroke who may be candidates for late recanalization therapies. These models provide an alternative approach to mismatch in predicting ultimate tissue fate.

Multivariate Dynamic Prediction of Ischemic Infarction and Tissue Salvage as a Function of Time and Degree of Recanalization

“…This may improve multiparametric imaging models using CTP that have been used to define infarct core and favorable penumbral pattern at the time of admission imaging with disregard of expected treatment time and that so far have failed to select patients who benefit from endovascular treatment over IV rt-PA alone. 21,37 It must be noted, however, that GLM coefficients derived in this study may be applicable only to the specific algorithm used for calculating perfusion parameters maps since different algorithms and vendor specific software are known to produce different perfusion values with different predictive power. 38 Furthermore, model coefficients are tailored to the data of our study population (endovascular-treated patients with major strokes due to proximal occlusion in the anterior circulation) and may not apply to a stroke populations defined by different inclusion criteria and treatment modes.…”

“…5,9,19 To combine the independent contributing effect of multiple variables on voxelwise infarct probability, multivariate image analysis has been explored including logistic regression or generalized linear model (GLM). 14,20,21 A multivariate imaging model that contains variables of timing and recanalization status opens the opportunity for dynamic estimation of infarction and salvageable tissue in the context of elapsing time and recanalization status after endovascular treatment. This is particularly important in light of evidence that growth of infarct lesions is heterogeneous and likely occurs beyond generally applied time windows for treatment in a large minority of patients.…”

2015 American Heart Association/American Stroke Association Focused Update of the 2013 Guidelines for the Early Management of Patients With Acute Ischemic Stroke Regarding Endovascular Treatment

“…Patients were divided into 2 subgroups by pretreatment CT or magnetic resonance imaging (MRI) into those with a favorable or those with an unfavorable penumbral pattern with the use of imaging criteria based on a previous study. 13 Patients were randomly allocated 1:1 to standard medical care or endovascular therapy (MERCI [Mechanical Embolus Removal in Cerebral Ischemia] or Penumbra device with optional intra-arterial r-tPA). Onset to groin puncture in the endovascular group was 381±74 minutes (mean±SD).…”

MR Rescue

“…3,8 The definition of the penumbral pattern differed from the more typical mismatch approaches used in other penumbral imaging trials and was based on a very complex voxel-by-voxel algorithm that included measures of the apparent diffusion coefficient, cerebral blood flow, mean transit time, and T max for the MRI model. The CT model substituted cerebral blood volume for the diffusion coefficient and added a nonimaging-based parameter: the baseline National Institutes of Health Stroke Scale score.…”

“…The CT model substituted cerebral blood volume for the diffusion coefficient and added a nonimaging-based parameter: the baseline National Institutes of Health Stroke Scale score. 8 It seems that these novel algorithms may not have performed as well as other more commonly used methodologies to identify salvageable tissue. 9,10 A benchmark for identification of penumbral patients is differential infarct growth between patients who achieve reperfusion and those who do not.…”